Magnetic field exposure is a generally concerned topic. In the past, there are a lot of researches carried out for the over-head line. However, there is not much study for the outdoor switching station. The aim of this dissertation is to establish a systematic method to evaluate the magnetic field strength of the high voltage outdoor switching station. The method includes the system data collection, power system modeling, magnetic field calculation and result analysis. In order to calculate the magnetic field in the human accessible area, a computer program has been developed. In order to verify the accuracy of the evaluation method, one of the typical 220kV outdoor switching stations in Hubei, China has been used for comparison. Magnetic field has been measured in the switching station at one meter above ground level. The switching station has also been modeled. The magnetic field calculation was based on the loading during measuring period. By comparing the magnetic field value of the measurement and calculation, it shows that the method is suitable for the switching station magnetic field evaluation. Hence, the method can be used to forecast the maximum magnetic strength during peak load. The maximum magnetic field strength can be compared with the health standard. The power utilities should then have a safety index on working environment of the operation personnel. If the field strength has exceed the health limit, the authority should provide guideline to their staff. Therefore, the systematic magnetic field evaluation method is an essential tool for the power utilities.